Manufacture of thiophenols



Patented May 2, 1950 UNITED S TAT-ES PAT ENT O F F ICE 2,506,416 MANUFACTURE OF THIOPHENOLS Everett E. Gilbert and EmeryJ Levin, New "York, N. Y., assignors'to'AlliedChernical &=' D-ye Corporation, a corporation of New York .No Drawing. Application october' 29, 1946, Serial No. 706,504

7- Claims.

procedures and accordingly are not capa'ble of producing .thiophenols "at low cost.

' One object of the present invention is to provide an inexpensive process 'formaking 'thiophenols by means of chemical reduction-employing easily available reducing'agents. .A further object of the invention is to provide a simple procedure for the production of thiophenols, which eliminates the numerous steps required by the complex procedures of the prior art. further object of theinvention is to provide'a'process applicable to the reduction of di-aryl disulfide's and di-aryl polysulfides of higher sulfur content such as the polysulfide mixtures obtained by "reacting diphenyl disulfide'with sulfur-or by react- 'ing diphen-yl sulfone with sulfur-to-produce polysulfide mixtures having an 'average sulfur'content in the neighborhood of 4 to 6 sulfur atoms permolecule. Stillfurther objects of the inventionwill-be apparent from the-following description and illustrative examples.

In accordance with the invention, a di-aryl 1polysulfide'(which term is used to include the'disulfide aswell as higher sulfides) "is'heated with a petroleum hydrocarbon material boiling above 250 C'., the heating step being carried out-attemperatures'of at least 250 C. rising 'finally to-be-- tween 350 C. and 400 C.

The process of the invention is applicableto the manufacture of thiophenols from "unsubstitutedand substituted 'di aryl polysulfides; e. 'g., 'diphenyl, ditolyl, dixylyl, dicumenyl, dipseudocumenyl, dinaphthyl, dichlorophenyl, di-o-di'chlorophenyl, 'di 1,2,4- trichlorop'henyl, =di-n1-chlorotolyl, di-'2,4-dichlo- -rotolyl, and di-chloro p-xylyl polysul'fides.

The proportioniof'petroleum hydrocarbon material to 'be employed as reducing agent'isquite flexible and since itsis' airelatively cheap'material, it is advantageous to employ an excess. In "the case of diphenyl 'polysulfides weight ratios'between about onepart and about .8parts of the reducingagentior'ieachiiiparts ofepolysulfide are dianthranyl, 'dibiphenyL.

preferred. In the-Tease of'the homologs, such as the adicumenyl :polysulfi'des, ratios of :reducing "agent to .polysulfide in the upper portion .ofzthe specified range are preferred and higher ratios may be advantageous.

When a thiophenol volatile at the reaction "temperatures is being produced, the thiophenol may be distilled oif from the reaction mixture and recovered by condensation. Removal of the thiophenol during the reaction avoids pyrolysis of the product and consequently leads'to higher yields than obtainable by carrying out theheating step without removing the product.

In the process of the invention the high-boilin'g petroleum hydrocarbons act as reducing agents convertin'gsulfur in the polysulfide to hydrogen .sulfide and providing the hydrogen atom necessary for addition to the thio-aryloxy radical (RS) to 'convert'it to thiophenol. It will be appreciated that the aryl radicals of the di-aryl .polysulfides and thiophenols may themselves serve "as reducing agents in the process. Such action is to be avoided, however, since it consumes a portion of the aryl radicals present in the qpolysulfide and results in correspondingly smaller yields of thiophenols.

In general, low-boiling hydrocarbons are relatively unsatisfactory reducing agents for the purposeacompared' to the high-boiling petroleum. derrivatives employed in accordance with the invention, and furthermore because of the'relative- .ly high "vapor pressure of such compounds and their dehydrogenation products, tend to contaminate the thiophenol product. For instance, whereas yields above 60% of theoretical may be :consistently'obtained using the reducing agents of the invention in the manufacture of thiophenol, a similar procedure using the relatively low-boiling hydrocarbon tetralin as a reducing agentresulted in a yield of only 30%, or only 5% "to 10% greater than the 20% to 25% conversion obtainable without any added reducing agent. "Moreover, as a 'result of dehydrogenation of the tetralin the product was found to be contaminated with substantial proportions of naphthalene.

While the invention is not limited to petroleum hydrocarbon materials of any particular type, it is preferred to employ those of the parafiiiiic or naphthenic or mixed base crudes.

Examples of suitable hydrocarbon materials for use in-accordance with the invention are No. 56fuel oil (a petroleum distillation residuenot distillable at atmosphericrpressure without decomposition and having an initialboiling point of about 310 to 320 C. with some decomposition), petrolatum, paraffin wax, and Pennsylvania Grade crude steam distillation residue. In general these materials comprise complex mixtures of hydrocarbons boiling substantially above 250 C. Paraffin wax, which is usually recovered from a condensate obtained in the steam distillation of petroleum, may contain small proportions of lower boiling materials but for the most part comprises normally solid high-boiling hydrocarbon compounds.

In the following discussion the invention is considered in particular relation to the-manufacture of thiophenol from diphenyl 'polysulfides. It will be understood, however, that the general principles involved are applicable to the manufacture of thiophenols from the other di-aryl polysulfides also.

The process of the invention is efiective for the reduction of diphenyl disulfide to thiophenol to obtain high yields in the neighborhood of 80% of theoretical. It is also applicable to the reduction of diphenyl polysulfides containing more than 2 atoms of sulfur per molecule to produce thiophenol in good yields. Representative polysulfides of this type are obtained by heating diphenyl monosulfide with sulfur in a ratio of about 4 atomic equivalents of sulfur per mol of the monosulfide at a temperature of 290 to 330 C. for 1 hours and then distilling off unreacted diphenyl monosulfide in vacuo to provide a polysulfide residue of approximately the composition (CsHs) 285%, or by reacting diphenyl sulfone with about 4 atomic equivalents of sulfur per mol at temperatures of 310 to 330 C. to provide a diphenyl polysulflde having the approximate average molecular formula (CeI-Is) 284. The process may be applied to crude polysulfide mixtures such as the oil obtained by heating benzene with a /1. mol ratio of sulfur chloride at 60-70 C. in the presence of ferric chloride, then washing and evaporating excess benzene.

The following examples further illustrate the process of the invention. Proportions are in terms of weight unless otherwise indicated:

Example 1 A mixture of 100 parts of diphenyl disulfide and 25 parts of petrolatum was heated in a still provided with a water-cooled condenser. The temperature of the still rose gradually and at about 270 C. thiophenol began to distill off. Heating and distillation were continued for about one hour, at the end of which period the yield thiophenol obtained in the condenser amounted to 79% of theoretical based on the diphenyl disulfide employed.

Example 2 A mixture of 146 parts of diphenyl polysulfide (CcI-I5)2S5%, obtained by reaction of 93 parts of diphenyl monosulfide and64 parts of sulfur and topping, as previously described, and 73 parts of petrclatum was heated in a still equipped with a Water-cooled condenser. When the temperature rose to 250 C., there was a copious evolution of hydrogen sulfide, and thiophenol began to condense in the condenser. Heating was continued to maintain the distillation of thiophenol, and in about 1 hours the temperature had risen to 360 C. (vapor temperature) and about 53 parts of thiophenol had been recovered in the condenser. This corresponds to a 48% yield based on total monosulfide used (54% based on polysulfide reacted).

4 Emample 3 A diphenyl polysulfide (Cal-19284, prepared by reacting one mol of diphenyl sulfone with 4 atomic equivalents of sulfur as previously described was employed. A mixture of about 1130 parts of this polysulfide and 284 parts of petrolatum was heated and distilled for 4% hours at temperatures rising gradually to about 375 C. The distillate was recovered and subjected to vacuum, distillation; 485 parts of thiophenol distillate boiling at to C. at 50 mm. of mercury absolute pressure corresponding approximately to a 55% of theoretical yield was obtained.

Example 4 parts of diphenyl olysulfide of the type employed in Example 3 and 50 parts of refined paramn wax were heated and distilled at atmospheric pressure in a period of 2 hours at a temperature rising from 270 to 360 C.-with condensation of distillata' The condensate was redistilled as' in Example 3, yielding 46.5 parts of thiophenol corresponding to a yield of approximately 60% of theoretical.

. Example 5 i I For purposes of comparison, a series of test was made under closely similar conditions involving as reducing agents petrolatum, parafiin wax, and 600W cylinder oil (Pennsylvania Grade crude steam refined residuum).

The procedure employed was as follows: 100 parts of phenyl polysulfide (CsH5)2S4, (prepared from diphenyl sulfone (1 mol) and sulfur (4 mols) as previously described) and 50 parts of the reducing agent were heated ina still equipped with a, Vigreaux fractionating column. Hydrogen sulfide started to evolve when the still temperature reached 230 C., and distillate began to form at 250 C. Heating was continued for a 2-hour period during which the still temperature rose to about 380 C. During this period the temperature at the top of the column was maintained between about 100 C. and about 200 C. The crude distillate was redistilled at atmospheric pressure, the fraction distilling at to C. being taken as the thiophenol fraction. The following yields were obtained:

Per cent Petrolatum 66 Parafiin wax 63 "600W cylinder oil 61 The same procedure employing 100 parts of No. 6 fuel oil as the reducing agent gave a yield 0 71% thiophenol.

We claim:

1. The method of making a thiophenol which comprises heating at a temperature of at least 250 C. rising finally to between 350 C. and 400 C. a mixture of a di-aryl polysulfide and a petroleum hydrocarbon material boiling above 250 C. and separating the resulting thiophenol from 1 residual hydrocarbon material.

' 2. The method of making a thiophenol which comprises mixing a diaryl polysulfide containing an average of 2 to 5 atoms of sulfur per molecule with at least one-fourth its weight of a petroleum hydrocarbon material distilling above 250 C. rising finally to between 350 C. and 400 C; and heating the mixture at a temperature of at least 250 C. and separating the resulting thiophenol from residual hydrocarbon material.

3. The process of the 'preceding'claim wherein the heating step is conducted at about atmospheric pressure and at temperatures rising gradually from about 250 C. to a final temperature between 350 C. and 400 C. and the thiophenol is distilled off during the heating step.

4. The method of making thiophenol which comprises heating at a temperature of at least 250 C. risin finally to between 350 C. and 400 C. ,a mixture of a diphenyl polysulfide and a petroleum hydrocarbon material boiling above 250 C., and removing thiophenol in vapor phase as thethiophenol is formed.

5. The method of making thiophenol which comprises heating at a temperature of at least 2502C. rising finally to between 350 C. and 400 C. a mixture of a diphenyl polysulflde containing an average of 2 to 5 atoms 1o; sulfur per molecule, and a petroleum hydrocarbon material boiling above 250 C., and removiijg thiophenol in vapor.

phase as the thiophenol-is'formed.

;6. The method of making thiophenol which comprises mixing a diphenyl polysulfide containingv an average 01' 2 to 5 atoms of sulfur per molecule with at least onef-fourth its weight of a paramnic petroleum hydrocarbon material distilling above 250 C. and heating the mixture at a 6 about atmospheric pressure at temperatures rising gradually from about 250 C. to a final temperature between 350 and 400 C., and distilling oi? thiophenol during the heating process.

7. The method of making thiophenol which comprises mixing a diphenyl polysulfide containing an average of 2 to 5 atoms of sulfur per molecule with from one-fourth to twice its weight of a parafiinic petroleum hydrocarbon material distilling above 250 C. and heating the mixture at about atmospheric pressure at temperatures rising gradually from about 250 C. to a final temperature between 350 and 400 C., and distilling off thiophenol during the heating process.

EVERETT E. GILBERT. EMERY J. LEVIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,174,248 Mikeska et a1 Sept. 26, 1939 2,230,542 Meinert et al Feb. 4, 1941 

1. THE METHOD OF MAKING A THIOPHENOL WHICH COMPRISES HEATING AT A TEMPERATURE OF AT LEAST 250*C. RISING FINALLY TO BETWEEN 350*C. AND 400* C. A MIXTURE OF A DI-ARYL POLYSULFIDE AND A PETROLEUM HYDROCARBON MATERIAL BOILING ABOVE 250*C. AND SEPARATING THE RESULTING THIOPHENOL FROM RESIDUAL HYDROCARBON MATERIAL. 